How do i connect a table?

I am using a templae (015_invoices different) and trying to make a version of it for my use.

I do not see how i can connect the table right.

Here is a screen shot of the working template fields you can see on the left it has a invoices pointing to the left but in the avalible items on the right it has none pointing to the left thay all point to the right.

How did that left pointing invoices get in their that seems to be what i need in my new version to get it working or at least part of it.
Thanks